SSCD can present with a conductive hearing loss that mimics otosclerosis and could explain some cases of persistent conductive hearing loss after uneventful stapedectomy. Audiometric testing with attention to absolute bone-conduction thresholds, acoustic reflex testing, VEMP testing, laser vibrometry of the umbo, and computed tomograph scanning can help to identify patients with SSCD presenting with conductive hearing loss without vertigo.

We present the first simultaneous sound pressure measurements in scala vestibuli and scala tympani of the cochlea in human cadaveric temporal bones. The technique we employ, which exploits microscale fiberoptic pressure sensors, enables the study of differential sound pressure at the cochlear base. This differential pressure is the input to the cochlear partition, driving cochlear waves and auditory transduction. In our results, the sound pressure in scala vestibuli (P SV ) was much greater than scala tympani pressure (P ST ), except for very low and high frequencies where P ST significantly affected the input to the cochlea. The differential pressure (P SV − P ST ) is a superior measure of ossicular transduction of sound compared to P SV alone: (P SV −P ST ) was reduced by 30 to 50 dB when the ossicular chain was disarticulated, whereas P SV was not reduced as much. The middle ear gain P SV /P EC and the differential pressure normalized to ear canal pressure (P SV − P ST )/P EC were generally bandpass in frequency dependence. At frequencies above 1 kHz, the group delay in the middle ear gain is about 83 μs, over twice that of the gerbil. Concurrent measurements of stapes velocity produced estimates of cochlear input impedance, the differential impedance across the partition, and round window impedance. The differential impedance was generally resistive, while the round window impedance was consistent with compliance in conjunction with distributed inertia and damping. Our technique of measuring differential pressure can be used to study inner ear conductive pathologies (e.g., semicircular dehiscence), as well as non-ossicular cochlear stimulation (e.g., round window stimulation and bone conduction)-situations that cannot be completely quantified by measurements of stapes velocity or scala vestibuli pressure by themselves.

The results suggest that superior semicircular canal dehiscence can affect hearing function by introducing a third window into the inner ear.

Background-Various authors have described conductive hearing loss (CHL), defined as an airbone gap on audiometry, in patients without obvious middle ear pathologic findings. Recent investigations have suggested that many of these cases are due to disorders of the inner ear, resulting in pathologic third windows.

Background-Although tympanic membrane perforations are common, there have been few systematic studies of the structural features determining the magnitude of the resulting conductive hearing loss. Our recent experimental and modeling studies predicted that the conductive hearing loss will increase with increasing perforation size, be independent of perforation location (contrary to popular otologic belief), and increase with decreasing size of the middle-ear and mastoid air space (an idea new to otology).

This report describes tests of a standard practice for quantifying the performance of implantable middle ear hearing devices (also known as implantable hearing aids). The standard and these tests were initiated by the Food and Drug Administration of the United States Government. The tests involved measurements on two hearing devices, one commercially available and the other home built, that were implanted into ears removed from human cadavers. The tests were conducted to investigate the utility of the practice and its outcome measures: the equivalent ear canal sound pressure transfer function that relates electrically driven middle ear velocities to the equivalent sound pressure needed to produce those velocities, and the maximum effective ear canal sound pressure. The practice calls for measurements in cadaveric ears in order to account for the varied anatomy and function of different human middle ears.

Despite a well-recognized clinical need for a material to replace missing or damaged vibratory connective tissue of the vocal fold, materials have yet to be engineered specifically for this purpose. Injectable hydrogels are particularly attractive because they would require a minimally invasive surgical procedure, could fill irregular defects, and could be designed to have viscoelastic properties similar to the normal tissue. We therefore synthesized a series of photo-cross-linkable hydrogels using hyaluronic acid (HA) as the starting material. The hydrogel precursors studied included HA modified with glycidyl methacrylate (HA/GMA), HA partially oxidized by sodium periodate (HAox) followed by GMA conjugation (HAox/GMA), and HA grafted with a synthetic polymer before introduction of GMA. The synthetic polymer employed was oligomeric poly(2-hydroxyethyl methacrylate) (P(HEMA)) with 31 mol % poly(N,Ndimethylacrylamide) (P(DMAM)), and the resulting hydrogel precursors were referred to as (HAox-g-P y)/GMA (y%: grafting percent). The macromonomers were characterized by GPC and 1 H NMR. Hydrogels were obtained by subjecting the aqueous macromonomer solutions to UV irradiation in the presence of a photoinitiator. Under physiological conditions HAox/GMA hydrogel exhibited the highest swelling ratio and degraded most readily, whereas (HAox-g-P 1.9)/GMA hydrogel swelled to a lesser extent and was most resistant to enzymatic degradation. Mechanical tests using an acoustic shaker yielded viscoelastic properties from 20 to 180 Hz. HAox/GMA hydrogel showed the lowest viscoelastic modulus and viscosity while (HAox-g-P 1.9)/GMA hydrogel exhibited the highest values. The interior structures of the fully swollen hydrogels examined by scanning electron microscopy (SEM) showed the presence of fibrous or porous morphology. The cell cytotoxicity study indicated that HAox/GMA macromonomer was cytocompatible at concentrations less than 0.2 mg/mL, and there was no loss of cells when encapsulated in (HAox-g-P 1.9)/ GMA photo-cross-linked network. These new hydrogels have potential as injectable formulations for regeneration of the vocal fold's mucosal layered microstructure.

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